Update 002_grammar_aligned_storage.cpp

Author: ls-Brynn

cpp_11/002_grammar_aligned_storage.cpp

@@ -1 +1,48 @@
-1
+#include <iostream>
+#include <type_traits>
+#include <string>
+ 
+template<class T, std::size_t N>
+class static_vector
+{
+    // properly aligned uninitialized storage for N T's
+    typename std::aligned_storage<sizeof(T), alignof(T)>::type data[N];
+    std::size_t m_size = 0;
+ 
+public:
+    // Create an object in aligned storage
+    template<typename ...Args> void emplace_back(Args&&... args) 
+    {
+        if( m_size >= N ) // possible error handling
+            throw std::bad_alloc{};
+ 
+        // construct value in memory of aligned storage
+        // using inplace operator new
+        new(&data[m_size]) T(std::forward<Args>(args)...);
+        ++m_size;
+    }
+ 
+    // Access an object in aligned storage
+    const T& operator[](std::size_t pos) const 
+    {
+        // note: needs std::launder as of C++17
+        return *reinterpret_cast<const T*>(&data[pos]);
+    }
+ 
+    // Delete objects from aligned storage
+    ~static_vector() 
+    {
+        for(std::size_t pos = 0; pos < m_size; ++pos) {
+            // note: needs std::launder as of C++17
+            reinterpret_cast<T*>(&data[pos])->~T();
+        }
+    }
+};
+ 
+int main()
+{
+    static_vector<std::string, 10> v1;
+    v1.emplace_back(5, '*');
+    v1.emplace_back(10, '*');
+    std::cout << v1[0] << '\n' << v1[1] << '\n';
+}